1. Field
The present disclosure relates generally to power converters and, in particular but not exclusively, relates to filtering input signals of the power converter.
2. Description of Related Art
Many electronic devices, such as cell phones, laptop computers, etc., use direct current (dc) power to operate. Conventional wall outlets generally deliver a high voltage alternating current (ac) power that needs to be transformed to dc power in order to be used as a power source by most electronic devices. Switched mode power converters are commonly used due to their high efficiency, small size, and low weight to convert the high voltage ac power to a regulated dc power. In operation, a switch is used to provide a desired output by switching at a variable duty ratio (typically, the ratio of on-time of the switch to total switching period) or by varying the number of ON and OFF cycles of the switch per unit time.
A switched mode power converter may also employ a controller which typically provides output regulation by sensing the output and controlling the switch in a closed loop. The controller may receive a feedback signal representative of the output and then vary one of the control parameters (e.g., duty ratio or the number of ON and OFF cycles of the switch per unit time) in response to the feedback signal to regulate the output to a desired quantity.
An input voltage of a power converter, also referred to as a line voltage, is usually a rectified and filtered ac voltage and the average value of the line voltage does not typically vary over time. The line voltage may have transient portions where the voltage level spikes (that is, fluctuates significantly over a short time period) due to several factors, such as power outages, power transitions in the large equipment on the same power line, malfunctions caused by the power company, etc. These voltage spikes produce corresponding transients (potentially having a large magnitude) in the input current of the power supply.
A controller of a switched mode power converter may have a sense terminal to receive an input sense signal, which is representative of a line voltage, in the form of a current to use for a multitude of purposes. In one example, a controller can use the input sense signal to realize various fault detection features, such as line overvoltage/undervoltage detection. In another example, a controller can adjust one of the control parameters, such as switching frequency, in response to the input sense signal to reduce the switching loss in a power converter.